The level of natural autoantibodies to IFN-gamma in varicella infection treated with antiviral drug Anaferon for children: A pilot study

Highlights

• Anti-IFN-gamma NAbs level in the healthy group is lower than the in infected patients.

• Anaferon for Children contributed to anti-IFN-gamma NAbs level decrease.

• Anti-IFN-γ NAbs level rises with increase of children age.

Abstract

Natural circulating antibodies (NAbs) to endogenous regulators have shown to be potential biomarkers in medicine. Due to the lack of reliable assays, only few of them have been well studied. To employ NAbs as biomarkers, an evaluation of changes over the course of a treatment is required. This paper describes our work to analyze the dynamics of NAbs titer to interferon-gamma (IFN-γ) among healthy children of different age and in patients with varicella infection receiving an antiviral drug Anaferon for children (AC, the API are highly diluted antibodies to IFN-γ) in comparison with placebo, and to correlate the findings with the treatment results. IFN-γ plays an essential role during varicella infection, and this fact causes the consequent increase of NAbs to IFN-γ level. The mean anti-IFN-γ NAbs level in the healthy volunteer group was 101 × 10³ U/ml (age: 0–15 years), which was significantly lower than the mean pre-treatment value in patients with varicella infection 167 × 10³ U/ml (age: 3–17 years). In the AC group, the NAbs level observed on days 5 and 10 decreased significantly to a level of 154 × 10³ U/ml, whereas in the placebo group it continued to rise in a time-dependent manner reaching 229 × 10³ U/ml on day 10. Our findings suggest that treatment with AC is characterized by “normalization” of the anti-IFN-γ NAbs levels in patients with varicella infection.

Introduction

Natural circulating antibodies (NAbs) found in the body have been a subject of a number of studies [1,2]. Especially many investigators have focused on NAbs specific for cytokines – a group of intercellular signaling proteins that regulate cell growth and development [3,4]. Cytokines (e.g. interleukines, tumor necrosis factors, interferons) are essential mediators of inflammation; corresponding specific NAbs are therefore recognized as important biologically active regulators of in vivo immune responses [5,6]. Continuous immunological processes, which occur also in healthy individuals, are accompanied by the generation of these NAbs in the blood. Substantially high levels of anti-cytokine NAbs are produced in patients with various infections, autoimmune diseases and tumors [[7], [8], [9], [10], [11], [12], [13], [14], [15], [16]].

A close relationship exists between the production of a specific cytokine and the generation of the corresponding NAbs during a disease [17]. For example, NAbs specific for the cytokine interferon-gamma (IFN-γ), which plays an important role in regulating viral replication, have been found in the sera of patients with various viral conditions [18,19], mycobacterial infections [[20], [21], [22], [23], [24], [25], [26]], as well as in the sera of healthy volunteers [17,18]. A number of studies have demonstrated the presence of anti-IFN-γ NAbs in immunocompetent individuals with intracellular infection while being healthy in all other respects [[27], [28], [29]]. It is assumed that these antibodies neither inhibit the antiviral and antiproliferative effects of IFN-γ nor prevent the binding of IFN-γ to its cell receptors. Yet they are able to inhibit IFN-γ-induced HLA-DR antigen expression on some cells. In animal models, anti-IFN-γ Nabs were shown to be able to play a role in immunoregulation and fine tuning of the amplitude and duration of the immune response [18].

The blood concentration of anti-IFN-γ NAbs rises during the acute phase of a viral disease and decreases as the recovery progresses [7]. The measured specific features of these antibodies depend on multiple factors such as the type of infection, the patient's age and immunological status, etc. In the acute phase, interferon-alpha and IFN-γ have proven to be detectable in high quantities in the sera of patients with varicella infection. IFN-γ has been shown to be released by T-cells isolated from individuals during primary in vivo sensitization and in vitro stimulation with varicella virus antigens [30,31]. Taking into account the fact that anti-IFN-γ NAbs may reflect IFN-gamma production [18], we assumed that the serum level of anti-IFN-γ NAbs would change along with disease progression. Therefore, our primary objective was to determine anti-IFN-γ NAbs levels at different disease stages of varicella infection. Furthermore, since NAbs levels were reported to be influenced by age [32,33], we examined them in three age groups of healthy volunteers: < 5 years, 6–11, and 11–15 years old.

Available evidence suggests that some ethnic groups are more liable to anti-IFN-γ NAbs generation (e.g., anti-IFN-γ NAbs are highly prevalent and recognized to be responsible for disease severity in Asian patients with disseminated nontuberculous mycobacterial infection [[21], [22], [23]2834]). Nevertheless, the presence of NAbs to IFN-γ should be considered in different infectious diseases, regardless of a patient’s age and ethnicity [35], particularly when IFN-γ is used in the treatment [36]. We also hypothesized that, apart from therapeutic IFN-γ, any other antiviral treatment with an effect on the immune system should have some influence on the anti-IFN-γ NAbs level.

Anaferon for children (AC) is an antiviral drug belonging to released-active compounds group [37,38] and based on highly diluted antibodies specific to IFN-γ, whose antiviral activity against different viruses has been demonstrated in previous non-clinical studies and clinical trials (among the latest are [39,40]. AC has been shown to be able to regulate the functional activity and production of endogenous interferons and to modulate the immune response depending on the initial body condition [[41], [42], [43], [44], [45], [46]]. The AC effect was shown to be specific, and mechanism of its action lies in the modification of IFN- γ conformational characteristics [37,45,47,48]. Our findings suggest that the efficacy of the treatment corresponds to a level of NAbs to IFN-γ in the patients’ sera.